Upper critical fields of periodic and quasiperiodic Nb-Ta superlattices

Abstract

Upper critical fields have been studied for two series of Nb-Ta superlattices grown by molecularbeam epitaxy with both periodic and quasiperiodic (Fibonacci sequence) layering. X-ray results are presented to characterize the nature and quality of the layering. Positive curvature in the perpendicular upper critical field (H, »), pronounced negative curvature near T, in the parallel upper critical field (H, 2~~), and dimensional crossover are observed in both types of samples. For quasiperiodic samples two upturns are observed in H, 2~~w ith decreasing temperature. These are shown to be associated with dimensional crossover occurring twice as the superconducting coherence length in the growth direction, g"samples the two length scales, 2d~b and d~b, that are present in these structures.

Strain Effects on the Crystal Growth and Superconducting Properties of Epitaxial Niobium Ultrathin Films

“…Superconducting thin films and multilayers have attracted the attention of the scientific community due to their geometry-specific properties as compared to bulk materials. − Multiple devices have benefited from the unprecedented properties of superconducting thin films such as the Josephson effect used in superconducting quantum interference devices (SQUID), superconducting single electron transistors, and even fundamental elements for quantum computation among others. In particular, devices such as stripline detectors for the detection of ions and superconducting single-photon detectors strongly benefit from the use of ultrathin superconducting thin films.…”

Comparative study of the sagittal elastic waves in metallic and semiconductor multilayer systems between periodic and Fibonacci superlattices

“…In fact several metallic Fibonacci superlattices have been produced in recent years: Nb/Cu [37][38][39], Mo/V [40], Nb/Ta [41], W/Ti [42] and Ta/Al [43]. We shall concentrate here in the W/Al system, which has been used in Schottky barriers and multilayer systems [44], although no Fibonacci superlattice has been grown to our knowledge.…”

Incoherent exciton trapping in self-similar aperiodic lattices

“…In the area of quasicrystalline matter the rapidly solidified alloys Al 80 Ni 14 Si 6 , Al 65 Cu 20 Mn 15 , Al 65 Cu 20 Co 15 , which are crystalline in two orthogonal directions and quasicrystalline along the other one, 11 are worth being mentioned. On the other side, regarding multilayered structures, after the first fabrication of Fibonacci 12 and Thue-Morse 13 semiconductor superlattices by Merlin and co-workers, the obtention of metallic 14,15 and superconducting quasiperiodic superlattices 16 and networks 17 has been reported.…”